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Leisure Batteries for Van Conversions (Complete Guide)

Updated: Sep 28

Batteries are EVERYWHERE, we use them EVERYDAY. Yet how many people really understand them? A campervan without batteries or electrics is... well, just a tin can. In this article, we are going deep on leisure batteries. We will look at the different types of leisure batteries (AGM, FLA, gel, lithium), how to install leisure batteries in your van conversion, how to calculate the size of battery, the best leisure batteries on the market, the lifespan you can expect from your batteries and how you can maximise that lifespan, and much more! By the end you will have a very thorough understanding leisure batteries and be ready for your own electrical installation! I'm Shane, I've been teaching people to convert campervans for many years, I'm the author of The Van Conversion Newsletter, the van conversion instructor at Udemy, and the proud owner of a beautiful self-build campervan called Beans. So let's jump in and have a look at leisure batteries for van conversions! van conversion!

Leisure batteries complete guide for van conversions

Items linked in this guide are affiliate links. By using these links, you are helping me to continue writing free educational van conversion content!

You can find the full list of van conversion supplies here.


Index

 

Note: Before we hop in, you might want to grab yourself a wiring diagram which you can get for free by signing up to The Van Conversion Newsletter (suggested, but not mandatory 🙂 - wiring diagram gets sent to you straight away).

 

What is a leisure battery?

A battery is a device that stores chemical energy, and converts it to electricity on demand. This is known as electrochemistry. To put it more simply: electricity is stored in batteries. Campervans are powered by leisure batteries - batteries which much provide a steady flow of current over a prolonged period. Leisure batteries for van conversions are typically 12v and are used to power everything from the fan and fridge to heater and lights.

Renogy lithium iron phosphate leisure battery

Starter batteries vs. leisure batteries

A starter (cranking) battery is what kicks your van into action when you turn the ignition. Starter batteries are designed to provide a big burst of energy (which the starter motor needs), the energy is supplied fast and can use as much as 20% of their total capacity per start. Once the engine starts up, the alternator recharges the starter battery so it’s ready to go for the next time you start up.


Leisure/Deep-cycle batteries in contrast release energy in a steady flow over a longer period - as mentioned above. They are designed to withstand hundreds/thousand of charging cycles.


The anatomy of a leisure battery (complex, so feel free to skip this section if you like 🙂)

A leisure battery is a plastic container, typically with six individual compartments inside.

Each compartment creates 2.12v, therefore creating 12.7V in total for a fully-charged battery.

Each compartment contains rows of positive and negative lead plates. These are setup in a grid so that lead oxide paste can be squeezed into all the little openings. Each plate is erected in a perforated piece of plastic called a separator.

In a leisure battery, these plates are thicker than in starter batteries; the separators also contain glass fibre sheets to squish against the lead oxide paste.


The glass fibre sheets help protect the batteries during constant re-charging (the paste can become loose and then completely come off from the lead grid).


The compartments of lead-acid batteries are filled with sulphuric acid (so be careful with these things!). Consequently, the plastic casing has a gas outlet for releasing hydrogen created during recharging. Though sealed lead-acid batteries do not have this outlet. Similarly, lithium batteries do not need to worry about any sulphuric acid.


Depth of discharge and battery cycles

Leisure batteries are designed to discharge power at a slow, steady rate over a long period of time. They are known as deep cycle batteries.


Leisure batteries can be discharged to a certain level, known as it's depth of discharge (DOD), hundreds/thousands of times in their lifetime.


A single discharge is known as a cycle. Lead acid batteries can (should) typically be discharged to 50%, whereas lithium batteries can be discharged far more (to about 80%)


We should be cautious never to completely drain our leisure batteries, and certainly never leave a battery in a completely discharged state. If recharging is delayed, sulfonation occurs. During sulfonation a white deposit forms on the battery’s plates. This is incurable and renders the battery useless.


Sometimes when sulfonation occurs the lead plates inside the batteries can fall over. When this happens you will see that the battery voltage falls to weird levels like 8v or lower. This is NOT normal, a leisure battery should never be able fall below ~11v.


It is possible to bring a battery back from an event like this by charging it up (typically with a very heavy charge initially). However, the more you allow your batteries to fall flat, the worse sulfonation will get until the batteries are rendered useless.


Leisure battery sulphination
Leisure battery sulphonation

Take good care of your batteries and your batteries will take good care of you 😇.


Types of leisure batteries (Lead-acid, AGM, Gel, Lithium, Lead-crystal)

At the highest level, there are two types of leisure batteries:


1. Lead-acid batteries

2. Lithium (LiFeP04) batteries


Lead-acid batteries

Gel vs. AGM vs. Flooded lead acid batteries

Lead-acid batteries are broken down into two subcategories:


a. Flooded (open/wet) lead-acid batteries

b. Sealed (VRLA) lead-acid batteries


Flooded lead-acid batteries emit gas (hydrogen) and thus need to be adequately ventilated. Occasionally they will need to be refilled with deionised water and must be kept securely upright! They are usually very cheap, but I do not recommend flooded lead-acid batteries for van conversions. They normally have a lifespan of 4-8 years with regular maintenance.


Note: If the batteries are overcharged they can emit sulphuric gas.


Sealed lead-acid batteries are sealed, thus they do not need any ventilation. Similarly, they do not need any topping up with deionised water. I recommend sealed lead-acid (or lithium) batteries for van conversions.


If we dive just a little deeper into sealed lead-acid leisure batteries, we find that we have two types:


i. Absorbed glass mat (AGM) batteries

ii. Gel batteries


AGM batteries are the cheapest type of sealed lead-acid battery. They are rugged and require no maintenance. They also charge well off solar power. They are the most popular type of battery for van conversions. They have a longer life than flooded lead-acid batteries and work better in colder conditions. Interestingly, AGM batteries can be used as starter batteries as well as leisure batteries. You can expect to get roughly 500 charge cycles (at 50% DOD) from an AGM battery.


Note: When recharging an AGM battery, the charge voltage must not exceed 14.4v (A battery charger or solar charge controller will handle this for you).


Gel cell batteries have all the benefits of AGM but with a longer life (if they are cared for!). However they are incredibly heavy. Gel cell batteries operate better in warmer and colder climates than AGM batteries. You can expect to get roughly 1000 charge cycles (at 50% DOD) from an AGM battery.


Note: When recharging an AGM battery, the charge voltage must not exceed 14.2v.


Lifespan of AGM vs. Gel cell sealed lead-acid batteries

As a rough rule of thumb, gel cell batteries have twice as many charge cycles as AGM batteries. Check out this graph below (super interesting 🤓). If we are careless with our batteries and discharge them 80-100% we absolutely destroy the lifespan of the battery (in both cases). In contrast, if we are kind to our batteries and only discharge them 25% our batteries will last a hell of a lot longer!


Keep those batteries charged boys and girls!

AGM vs Gel charge cycles vs. depth of discharge

Lithium (LiFeP04) batteries

I won't beat around the bush, lithium batteries are awesome. Lithium batteries provide as much energy as lead-acid batteries for a quarter the weight and smaller! 🤯 The lifespan (number of charge cycles) of a lithium battery is up to 5+ times that of a lead-acid battery and has a depth of discharge of 80%.


There is no liquid in a lithium battery so they can even be mounted upside-down. They require little maintenance and charge much faster than lead acid batteries.


Surely there's a catch? Yep 😢 The pricetag. They are up to four times the price of a lead-acid battery. However in this van converter's humble opinion: well worth the price. Only recently, I removed four sealed lead-acid batteries (520Ah) from my van and replaced them with a single 200Ah lithium battery; and I couldn't be happier.


Given the graph below, with a DOD of 50%, we can expect to get ~1150 charge cycles from our lithium leisure battery. Though, with high quality Lithium batteries you can expect 2000-4000 charge cycles.

Lithium leisure battery charge cycles vs depth of discharge

It's worth noting that Lithium batteries function a lot worse in very cold temperatures when compared to lead-acid.


Lead-crystal batteries

I'm going to give these rarer batteries an honorable mention. They are not popular in van conversions yet because they are relatively new. They also have no liquid meaning there is no risk of spillage or sulfonation. They were originally designed by UPS and are around twice the price of a regular lead-acid battery.


Lead-crystal batteries charge twice as quick a lead-acid, have more charge cycles, and appealingly can function in very extreme temperatures.


Categories (class) of leisure battery

A leisure battery is certified class A, B, or C. A lasts the longest and is designed for frequent use, C lastest the shortest length of time and is designed for infrequent use. A has more lead, C has less lead.

  • Category A is for higher storage capacity for people who frequently use their campervans away from electrical hook-ups

  • Category B are aimed at those who frequently use sites with hook-up facilities, but require a greater battery capacity.

  • Category C is for users that require a lower capacity battery, just to cover basic operation of their appliances for short periods away from a hook-up

It is worth pointing out that Category A batteries will be significantly heavier than their C Counterpart. Weight is a good measure of quality with lead-acid batteries; the heavier, the better.


I would suggest you grab yourself a nice, heavy category A leisure battery.


Charging profiles of leisure batteries


Charging profiles of leisure batteries normally follow three stages: bulk, absorption and float. The charging limits differ between the different battery types.

  • Bulk: a fast, constant current charge up to ~80% State of Charge (SoC)

  • Absorption: much slower, constant voltage charge to reach 100% SoC

  • Float: a constant voltage charge which maintains 100% SoC by counteracting self-discharge

Leisure battery charging profiles (lithium vs lead acid)

Note how different batteries charge best at different voltages. Lead-acid batteries (AGM, Gel, FLA) in particular require large voltages in the constant and current stages of the charge profile. Lithium batteries are the inverse - they require less power initially and gradually ramp up.


It is also worth pointing out that the current (amperage) works in the opposite way - at the beginning of the charge profile, the amperage starts high and gradually gets lower.


A solar charge controller or battery charge ensures that the voltage and amperage matches the expecting charge stage of the battery. It is paramount that is does its job correctly. For example, if we had four solar panels wired in series (74.4v) wired directly to our leisure batteries, we could be in for a very, very dangerous time indeed. The sulphuric acid will begin to boil and the plastic casing will start to melt... 😲


How to maximise the life of your leisure batteries

  • MOST IMPORTANT: Keep your batteries nice and charged up (>50%) to increase the number of charge cycles.

  • NEVER let your batteries remain fully uncharged or you risk sulfonation which is an incurable disease for batteries.

  • Before mounting terminal clamps on the battery terminals, apply a thin layer of Vaseline to the battery’s terminals.

  • If you’re not currently using your campervan, make sure you use a trickle charger (keep it plugged into mains) to stop the leisure battery from completely losing charge.

  • If you are using flooded lead-acid batteries, make sure you regularly check that the electrolyte level covers the lead plates on the battery. If it doesn’t, make sure you top it up with deionised water.

  • Every now and then check that the gas relief tube is fitted securely.

Factors affecting the performance of leisure batteries

Temperature: The colder the temperature, the poorer the performance of the battery. The Ah rating stated on a battery is based on a temperature of 25C, with each degree lower causing a 1% drop in performance. For example, an 110Ah battery operating in 15C temperature will actually perform as a 100Ah.


Age: Most leisure batteries will not last more than ~five years and experience a decrease in performance over time.


Power consumption: If a large number of appliances (high wattage) are run from the leisure battery, it will discharge quicker and therefore need to be recharged more often. This frequent recharging will cause the battery to degrade sooner.


Category: As mentioned before, Category B and C batteries will not last as long as Category A batteries due to their being less lead in the battery.


How to calculate the size of leisure batteries for your van conversion


Quick note: For an in-depth explanation of electricity as it relates to van conversions (Volts, Amps, Watts, Fuses, Wire sizes, AC/DC, Solar, batteries), I highly suggest you check out this complete guide. Below, I will give an overview of what is covered in that article.


To calculate our battery size we will be filling out a load sheet that looks like the image below. You can download a blank template of this load worksheet here.

van conversion appliance load watt hour spreadsheet

  1. In order to figure out the size our leisure batteries need to be, we will first need to figure out all the appliances we will have in our campervan. List out all the electrical appliances you want in your van in the worksheet.

  2. Enter the quantity you will have of each item.

  3. Enter the Voltage of the appliances; most appliances will be 12v DC, though some will be 230v AC (eg. the laptop is charged through the mains plug sockets).

  4. Enter the Amps of each individual appliance (you can find this on the spec sheet for the appliance)

  5. Total amps will auto populate (quantity X amps)

  6. Watts will auto populate (Total Amps X Volts)

  7. Enter the number of hours per day you estimate you will use the appliance (Note: fridges turn on and off throughout the day, so you don't need to enter 24 hours for your fridge)

  8. Total watt hours will automatically be populated for you.


The output at the very the bottom of this worksheet is the total watt hours (Wh) that will be used given all our appliances.


van conversion total watt hours

We will quickly convert the Watt hours (Wh) to Amp hours (Ah) as Ah is more commonly used for sizing 12v leisure batteries.

The formula to convert Wh to Ah is: Ah = Wh / V

So given our estimated loads, Ah = 1185Wh / 12. Which gives us ~98Ah


In other words, we can expect to use 98Ah of battery power per day in our campervan. However I want to be able to be off-grid for at least two days, so I'm going to multiply the Ah by two to give me 196Ah.


One further caveat; remember we can only discharge lead-acid batteries to 50%, so we will actually need TWICE our calculated Ah. 2 X 196Ah = 392Ah. Hence the reason why I had 520Ah of battery power up until recently.


How long does it take to charge leisure batteries (solar panels, split charge relay, shore power)?

There are three ways of charging leisure batteries in a campervan:

  1. Solar panels

  2. Split charge relay (connect to the alternator of the vehicle so you charge up while driving)

  3. Shore power (plug into mains)

So, let's figure out how long it will take to recharge our leisure batteries with solar panels, a split charge relay, or shore power.


Say for argument's sake we have 392Ah of leisure battery storage; at any given time we will discharge it 50% and so we will need to fill 196Ah. Let's quickly convert this back to Wh for ease of calculation. The formula is Wh = Ah * V, which would give us 2304Wh.


In order to figure out how long it will take to fill the batteries for each source, all we need to figure out it the Wattage coming from that source.


How long does it take to charge leisure batteries from solar panels?

Let's say we have four 100w solar panels on our van roof, giving us a total of 400w power. We know we have to fill up 2304Wh of battery using 400W of solar power. So: 2304Wh / 400 watts = 5.8 hours

Not bad obama

However, solar panels typically only output 70% of the rated wattage. This is primarily due to the angle of the sun. So: 2304Wh / (400W * 0.7) = 8.2 hours


How long does it take to charge leisure batteries from a split charge relay?

The alternator typically delivers 65W of electricity to the leisure battery. Using the same math as above, 2304Wh / 65w = 35 hours. One way to increase the speed of the charge with a split charge relay is to use a DC to DC charger instead like this one. Expensive but worth it.


How long does it take to charge leisure batteries from shore power?

In order to charge our leisure batteries off mains we will need an AC to DC battery charger like this one. The battery charger regulates the flow of electricity to the batteries and converts the AC into DC.


If for instance if we have the Victron 30a IP22 battery charger, we can expect to fill our 196Ah batteries in 196Ah / 30a = 6.5 hours


How to install leisure batteries in a van conversion

You can get a complete wiring diagram when you sign up to The Van Conversion Newsletter. The diagram shows you how to wire up your batteries and everything else! I send out the wiring diagram straight away.


Leisure batteries for van conversions are typically wired in parallel. This keeps the voltage the same (12v), but increases the Amperage (or Amp hours). To wire leisure batteries in parallel we simply connect all the positive terminals and all the negative terminals in a daisy chain fashion. Like the diagram below!

Leisure batteries wired in parallel

In my van conversion I used 0AWG cable to connect all the batteries together, giving myself some wiggle room. You can learn all about wire sizing in this article.


Connect the leisure batteries to positive and negative bus bars

Instead of running all our appliances directly to the leisure batteries, we will instead run them to bus bars - which keeps our wiring nice an neat! We run a single positive and negative cable from each busbar to the leisure batteries. I used 0AWG cable for this (Very beefy 🐮).

Connecting bus bars to batteries

On the way to the bus bars, we are going to chuck an isolator switch on the positive line (a giant switch that will cut-off all electrics if switched). We will also add a 250a fuse (or similar) onto the cable as a last ditch effort to protect the batteries in case of electrical overload.


250a inline ANL fuse
250a inline ANL fuse

Some people will opt for a single leisure battery, while others will opt for multiple batteries, thus increasing storage capacity. If you are using multiple batteries, make sure you wire them in parallel to keep the voltage at 12v; if you wire in series the voltage increases as a factor of the number of batteries attached. I used two 130aH leisure batteries.

Wiring two leisure batteries in parallel
Wiring two leisure batteries in parallel

Don't forget to ground your batteries!

It's very important that you ground your leisure batteries! It's very simple, you can learn how to do it here.


How to check the charge level of your leisure batteries

There are three ways of checking the charge level of your leisure batteries:

  1. Voltmeter

  2. Battery monitor

  3. MT50 solar monitor

To determine how full a leisure battery is, we use Volts. Here is the table of V olts and what they equate to:

  • 12.7V or over: 100%

  • 12.5V: 75%

  • 12.4V: 50%

  • 12.2V: 25%

  • 12V or under: Discharged

Voltmeter

To see the charge of your batteries with a voltmeter, simply touch the positive node of the voltmeter to the positive terminal of the battery, and similarly the negative to the negative.

voltmeter for leisure batteries

If the voltmeter gives a reading of >12.7v you are fully charged!


Battery monitor

A more permanent way of checking the levels of our batteries is to hook up a battery monitor. It gives us lots of interesting metadata about our batteries.

battery monitor for leisure batteries

To install one of these, we will need to install a 'shunt' on the negative line leading to the batteries. We wire up three small negative cables from the shunt to the battery monitor and also wire our battery monitor in DC positive.


MT50

The MT50 is a device that comes with the Epever solar charge controller. It also gives a bunch of helpful metadata on your batteries and is far easier to install than a battery monitor! If you have solar power, I'd just monitor your batteries with this :) Alternatively, you can use the very cool bluetooth monitor from Renogy that connects with your smartphone.

MT50 battery monitor

Conclusion

I truly hope you found this explanation of van conversion leisure batteries useful! That was a lot of information! I think you now know EVERYTHING THERE IS TO KNOW about leisure batteries. You are now well equipped to build out a kickass electrical system in your own self-build campervan! Don't forget to subscribe to The Van Conversion Newsletter for everything you need to get started with your own van conversion (I'll send you a free wiring diagram when you sign up).


If you're converting a van but unsure of how to do it, you could also check out the Van Conversion Course on Udemy. In the course, you'll learn directly from me how to convert a van into your dream home - no prior experience needed!


Until next time,

Shane ✌️